Substation-circuits



W. H. MARTIN.

SUBSTATION CIRCUITS.

I APPLICATION FILED DEC. 19, I918: 1 57 29 Patented NOV- 2, 1920.

INVENTOR: BY WHMartzn W TdRN E Y UNETE!) fiTA'lIiS PATENT OFFlCE.

WILLIAM H. Iv'IABTIN, OF NEW YORK, N. "521, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION 0:3 NEW YORK.

SUBSTATION-OIRCUITS.

Application filed December 19, 1918.

To all EU/1077b it may concern:

B6 ithnown that ii, lVILLmrr H. MARTIN, residing at New York, in the county of Bronx and State of New York, have invented certain improvements in Substation-Circuits of which the following is a specification.

ihis invention relates to substation tele phone circuits and more particularly to sub station circuits of the anti-side tone type.

(inc of the objects of the invention is to so arrange an anti-side tone set of the type in which an electromagnetic receiver is employed that when the direct current path through the transmitter and receiver is opened by means of the switclnhoolr, an undesirable click will not be produced in the receiver. Other and furth r objects of the invention will, however, more fully appear in commotion with the detailed description of the invention hereinafter given. I

The objects of the invention as herein disclosed are secured. by so arranging the con tacts of the switchhook that when the switclihooh is operated to open the circuit, the direct current path through the receiver and transn'iittcr will be opened an instant before the connection between. the receiver and an auxiliary path including a condenser opened, so that the energy stored up in tile receiver and transformer will have an opportunity to gradually discharge through the auxiliary circuit.

The invention may now be understood from the following description when read in connection with the accompanying drawing, the figure of which illustrates a circuit arrangement of a preferred embodiment of the invention.

The substation of this invention comprises, among other elements, a transmitter [l an electromagnetic receiver R, an auxiliar resistance X and a three winding transformer including windings l, 2 and The transmitter T and the receiver R are arranged in series with winding 1 of the transformer, the three elements being bridged across the line terminals d and 5. The receiver is shunted by a path including wind" ing 2 of the transformer and the auxiliary resistance X which, in practice, may be incorporated in the winding 2. An auxiliary path 6 is arranged in shunt with the transmitter T said auxiliary path including winding ot the transformer and a con-- Specification of Letters Patent.

Patented Nov, 2, 1920.

Serial No. 267,517.

denser 7 to prevent the passage of a direct current through this auxiliary circuit. The ringer 8 is connected from the line terminal to the terminal 9 of the winding 3. In order to control the direct current path the switchhoolc ll) is provided, said switchhook controlling contacts 11 and 12, the former of which opens the direct current circuit by disconnecting the transmitter 10 'from the parallel paths through resistance X and receiver It. Contact 12 controls the connection of said paths to the auxiliary path 6. The contacts of the switchhoolr are so arranged that contact 11 is opened before con tact 12.

The arrangement of the transmitter, receiver, auxiliary resistance, line and transformer above described results in an antiside tone substation circuit of the general type disclosed in certain patents granted to i leorge A. Campbell under date of January 22, 1918, and the general theory and operation of the anti-side tone circuit is fully disclosed in said patents. Furthermore, as the specific arrangement of the fundan'iental elements of the substation is fully disclosed in an application of K. S. Johnson Serial No. 210,265, filed rlanuary d, 1918, it is thought to be unnecessary to describe the de to red ogeration of the circuit except in so far as it relates to the prevention of clicks in the electromagnetic receiver. The operation whereby undesirable clicks are prevented is as follows:

Normally. direct current flows from the line to terminal l, through the winding 1 and thence in parallel both through electromagnetic receiver R, and through winding 2 and auxiliary resistance X in series, thence over switchhook contacts 12 and 11, through the transmitter 10 to terminal 5 and back to the line. Since condenser 7 is included in the auxiliary path 6 no direct current flows through. this path. Upon operating the switchhook 10, as for instance to recall the operator, the contact 11 is first opened, the contact 12 remaining closed for an instant so that the energy stored up in the electromagnetic receiver and trans-former winding has an opportunity to discharge over the contact 12 and through the winding 3 and condenser 7. As this discharge is gradual and may take place before the contact 12 opens, no undesirable click results in the re ceiver R,

ll hile this arrangement is illustrated in what is believed to be its most desirable form, it will be obvious that the general rinciples herein disclosed may be embodied in many other organizations widely differentrfrom what is illustrated without depart ing from the spirit of the invention as defined in the following claims.

What is claimed is: r

1. In a substation set,- a transmitter and a receiver connected in circuit so that direct current flows through both instruments, an auxiliary path over which variable current can flow from the receiver to the line, and a circuit controller so arranged as to open the direct current path through the transmitter and receiver before opening the connection between the receiver and auxiliary path, whereby the energy stored in the receiver may discharge through the auxiliary path.

2. In a substation set, a transmitter and a receiver connected in circuit so that direct current flows through both instruments, an auxiliary path including a condenser in shunt with the transmitter, and a circuit controller so arranged as to open the direct current path through the transmitter and mitter and receiver, and a winding in said auxiliary path, and a circuit controller so arranged as to open the direct current path through the transmitter and receiverbefore stored in the receiver may discharge through the auxiliary path.

4. In a substation set, a transmitter and a receiver connected in circuit so that direct current flows through both instruments, an auxiliary resistance in shunt with the receiver, an auxiliary path including a condenser in shunt with the transmitter, a transformer including a winding in series with the transmitter and receiver and a winding in; said auxiliary path, and a circuit controller so arranged as to open the direct current paththrough the transmitter and receiver before opening the connection between the receiver and auxiliary path, whereby the energy stored in the receiver may discharge through the auxiliary path.

5. In a substation set, a transmitter and a receiver connected in circuit so that direct current fi'ows through both instruments, an

auxiliary resistance, an auxiliary path including a condenser in shunt with the transmitter, a transformer including a winding in series with the transmitter and receiver, a winding in said auxiliary path, said auxiliary resistance and a third winding of said trans-former being arranged in series-shunt relation with said receiver, and a circuit controller so arranged as to open the direct current path through the transmitter and receiver before opening the connection between the receiver and auxiliary path, whereby the energy stored in the receiver may discharge through the auxiliary path.

In testimony whereof I have signed my name to this specification this 17th day of December 1918.

WILLIAM H. MARTIN. 

